Flow control valve

ABSTRACT

A flow-metering valve assembly is provided for vehicle fuel tanks. The assembly includes a valve housing having an interior wall configured to define a chamber having an inlet and an exhaust outlet. The interior wall provides a first flow-metering surface situated in close proximity to the outlet. A spring-biased pressure-relief element is situated in the chamber and includes a valve member having an inner surface confronting the inlet and an upstanding skirt attached to the valve member. The skirt has a distal portion extending in an outward direction toward the outlet means to provide a second flow-metering surface. The first and second surfaces cooperate to define a variable flow-metering orifice therebetween. The second flow-metering surface is moved in relation to the first flow-metering surface in response to relative movement of the valve member and the valve seat to vary the size of the variable flow-metering orifice so that the flow of pressurized fuel vapor through the variable flow-metering orifice is metered in accordance with a predetermined specification.

This is a division of application Ser. No. 935,814 filed Nov. 28, 1986,now U.S. Pat. No. 4,715,403.

The present invention relates to fuel system valves, and particularly toa flow control valve for regulating the discharge of pressurized fuelvapor from a fuel tank. More particularly, the present invention relatesto a valve assembly having a pressure-relief valve and a flow-meteringorifice in the assembly that changes in size in a predictable mannerduring operation of the valve to control the flow of fuel vapor throughthe assembly in accordance with a predetermined specification.

Vehicle fuel systems are known to include pressure-relief valvesmountable on either fuel tanks or filler necks. In general, the ventingportion of these conventional valve assemblies has included apressure-relief valve positioned in a vent passageway having a surfaceexposed to the pressure in the tank and a yieldable control springurging the pressure-relief valve normally to close the vent passageway.In response to a predetermined superatmospheric pressure, thepressure-relief valve is urged in opposition to the control spring toopen the vent passageway.

In practice, it is desirable to provide a safety pressure-relief valvethat opens quickly in response to a small change in the pressure fuelvapor in the fuel tank. Valve opening time can be reduced by increasingthe force applied to the valve at constant pressure. Such an increase istypically obtained by enlarging the outlet opening in the fuel tanknormally closed by the valve so that the pressure in the fuel tank actsover a larger surface area, thereby increasing the lifting force appliedto the valve. While such a large diameter tank outlet opening isinitially necessary to provide a quick-opening valve capable ofimmediate venting, in certain circumstances, this large-diameter openingcan vent fuel vapor into the atmosphere at a flow rate in excess ofdesign specifications while the companion valve is open.

A valve system including means for controllably metering the flow rateof pressurized fuel vapor discharged during venting activity would avoidshortcomings of known valve systems. Conventional valves are notequipped to meter the flow of pressurized fuel vapor from the fuel tankor other fuel system components at a selected variable rate inaccordance with a predetermined specification matching, for example, theflow rate of pressurized fuel vapor discharged by the valve and fueltank pressure. Such a specification is often represented by a plot ofthe volumetric flow rate of discharged fuel vapor as a function of themagnitude of pressure in the fuel tank.

In many cases, it is desirable to vary the fuel vapor flow rateautomatically during operation of the valve. For example, in order tomeet a selected flow rate/tank pressure specification, it may benecessary to reduce the flow rate of fuel being discharged by the valveif the tank pressure increases while the valve is open. However, thesize of the flow discharge orifice in conventional valve assembliestypically does not decrease to vary the flow of pressurized fuel vaportherethrough in accordance with a predetermined flow schedule at tankpressure levels of greater magnitude than the tank pressure necessary toactuate the valve initially. While conventional valve assemblies operateto vent excessive fuel vapor pressure from the fuel tank, they do notprovide means for selectively increasing and decreasing the flow ofpressurized fuel vapor discharged from the fuel tank as a function ofthe magnitude of pressure in the fuel tank.

One object of the present invention is to provide a pressure-reliefvalve assembly that meters the volumetric flow rate of pressurized fuelvapor discharged therethrough in accordance with a predeterminedspecification.

Another object of the present invention is to provide a pressure-reliefvalve assembly that will open quickly in response to a small change inpressure to provide immediate venting and thereafter meter the dischargeof pressurized fuel vapor at either a low flow rate, a high flow rate,or a predetermined non-linear combination of high and low flow rates, asa function of the magnitude of pressure existing in the fuel tank.

According to the present invention, a flow-metering, pressure-reliefvalve assembly is provided for vehicle fuel tanks or other components ina vehicle fuel system. The assembly includes a valve housing having aninterior wall configured to define a chamber, inlet opening means foradmitting fuel vapor into the chamber, and outlet opening means forexhausting fuel vapor from the chamber, a valve seat situated in thechamber to surround the inlet opening means and attached to the valvehousing, and a pressure-relief element in the chamber.

The pressure-relief element includes a valve member having an innersurface confronting the inlet opening means and an upstanding skirtattached to the valve member. Biasing means is provided for yieldablybiasing the valve member against the valve seat normally to close theinlet opening means.

The assembly provides a novel system for metering the flow ofpressurized fuel vapor through the assembly to control and regulate thepressure in the fuel tank for a variety of purposes. The interior wallprovides a first flow-metering surface situated in close proximity tothe outlet opening means. The upstanding skirt has a distal portionextending in an outward direction toward the outlet opening means inspaced relation to the first flow-metering surface. The distal portionprovides a second flow-metering surface which cooperates with theopposite first flow-metering surface to define a flow-metering orificeof variable size therebetween. The first and second flow-meteringsurfaces have contoured shapes that are configured to meter the flow ofpressurized fuel vapor through the orifice in accordance with apredetermined specification. This specification matches the flow rate offuel vapor exhausted from the chamber through the outlet opening meansto the magnitude of pressure exposed to the inner surface of the valvemember.

The cross-sectional size of the flow-metering orifice at a certain tankpressure is determined by a variety of factors, most notably, relativemovement of the first and second flow-metering surfaces and the contouror exterior shape of those surfaces. Relative movement of the first andsecond flow-metering surfaces acts to vary the size of the orifice. Thisvariance in size affects the vapor discharge capacity of the assembly byrestricting or enlarging the cross-sectional area of the orifice.Careful selection of the shape of each flow-metering surface makes it ispossible to modify the size of the orifice. In one embodiment, due tothe shapes of the flow-metering surfaces, the cross-sectional area ofthe orifice can be enlarged even though the valve member is moving awayfrom its seat, and, the cross-sectional area of the orifice can bereduced even though the valve member is moving toward its seat. Thus,the shapes of the spaced-apart flow-metering surfaces can be selectedduring a design stage to, in essence, "program" the discharge capacity(i.e. flow rate) of the assembly as a function of tank pressure inaccordance with a predetermined specification.

In particular, the predetermined specification matches a series of fuelvapor pressures occurring in the fuel tank with a corresponding seriesof flow rates of pressurized fuel vapor discharged from the fuel tankthrough the flow-metering orifice to define a selected flow-pressureschedule.

In preferred embodiments, the valve member divides the chamber into afirst portion communicating with the fuel tank via the inlet openingmeans and a second portion communicating with the outlet opening means.Pressurized fuel vapor in the first portion in excess of a predeterminedamount acts against the inner surface of the spring-biased valve memberto move the valve member away from its seat, thereby moving the secondflow-metering surface relative to the first flow-metering surface. Thesecond flow-metering surface is moved to a predetermined position in thevalve chamber associated with the magnitude of the fuel vapor pressurein the first valve chamber portion. Such movement causes the orifice tohave a flow capacity sufficient to discharge pressurized fuel vaportherethrough in accordance with the predetermined specification.

One feature of the present invention is the provision of a flow-meteringorifice of variable size between the interior wall of the valve housingand the pressure-relief valve member. This orifice advantageouslychanges in size during operation of the assembly as a function of themagnitude of pressure in the fuel tank to control the flow of fuel vaporthrough the assembly, thereby regulating the pressure in the fuel tank.

Another feature of the present invention is the cooperation of a firstflow-metering surface on the fixed valve housing and a secondflow-metering surface on the movable pressure-relief valve to define avariable flow-metering orifice. The first and second flow-meteringsurfaces have contoured shapes that are configured to match theinstantaneous size of the orifice to the magnitude of pressure existingin the first valve chamber portion in accordance with a predeterminedspecification. Thus, the particular contour of the flow-meteringsurfaces may be advantageously selected during an initial design stageto produce a selected flow/pressure schedule suitable to meetsubstantially any predetermined specification. Advantageously, aninfinite number of flow/pressure relationships are obtainable due tothis feature merely by altering the configuration of the first and/orsecond flow-metering surfaces.

Additional objects, features, and advantages of the invention willbecome apparent to those skilled in the art upon consideration of thefollowing detailed description of preferred embodiments exemplifying thebest mode of carrying out the invention as presently perceived.

BRIEF DESCRIPTION OF THE DRAWINGS

The detailed description particularly refers to the accompanying figuresin which:

FIG. 1 is a sectional detailed view of one embodiment of a valveassembly in accordance with the present invention;

FIG. 2 is a sectional detailed view of another embodiment of a valveassembly in accordance with the present invention;

FIG. 3 is a sectional detailed view of yet another embodiment of a valveassembly in accordance with the present invention; and

FIG. 4 is a sectional detailed view of still another embodiment of avalve assembly in accordance with the present invention.

DETAILED DESCRIPTION OF THE DRAWINGS

In the embodiment illustrated in FIG. 1, a valve assembly 10 includes ahollow valve housing 12 that is mounted on a wall 14 of a fuel tank 16.Valve assembly 10 is positioned in communication with an aperture 18formed in wall 14. The valve assembly 10 functions to meter the flowrate of pressurized fuel vapor discharged to the atmosphere or otherpoint of use in accordance with a predetermined flow rate/tank pressurespecification. As a result of this metering function, the valve assembly10 regulates the pressure within fuel tank 14, thereby controlling themaximum fuel tank pressure.

The valve housing 12 includes an interior wall 20 and an outlet passage22. The interior wall 20 and outer surface 24 of wall 14 cooperate todefine vapor discharge chamber 26. Fuel vapors are admitted into chamber26 through the aperture 18 and exhausted therefrom through the outletpassage 22. Thus, aperture 18 provides an inlet opening for the valveassembly 10.

A pressure-vacuum valve 30 is installed in chamber 26 to regulatepressure in the fuel tank 16. The pressure-vacuum valve 30 includes agasket 32, an umbrella valve 34, a valve member 36, and a spring 38. Thegasket 32 is positioned on outer surface 24 of wall 14 to surroundaperture 18. Gasket 32 includes an inwardly projecting annular valveseat 39.

The valve member 36 includes a central portion forming fourcircumferentially spaced fluid-conducting apertures 40 and a peripheralring flange 42 defining an exterior side wall 44. Side wall 44 ispositioned in close proximity to a lower portion 46 of interior wall 20to define an annular passageway 48 therebetween. The valve member 36further includes an upstanding skirt 50 fixed to a top surface 52 of thecentral portion. The skirt 50 includes a distal end 54 positioned inclose proximity to a downwardly-facing portion 56 of the interior wall20.

The umbrella valve 34 is made of a pliable material and includes a stem58 that is installed in a central aperture formed in the valve member36. Valve 34 also includes a resilient valve cover 60 that is positionednormally to cover the lower opening of each of the apertures 40 formedin the valve member 36. The spring 38 is installed in the chamber 26between wall 56 and the top surface 52 of the valve member 36 in aposition surrounding skirt 50. Thus, the spring 38 provides means foryieldably urging the ring flange 42 into seating engagement with thevalve seat 39 provided by gasket 32.

The flow of fuel vapor discharged through outlet passage 22 is meteredbetween an orifice 62 established by interior wall 20 and skirt 50 toregulate the pressure in chamber 26 in fuel tank 14. Downwardly-facingsurface 56 of interior wall 20 is configured to provide a firstflow-metering surface 64a while distal end 54 of skirt 50 is configuredto provide a second flow-metering surface 66a. The two flow-meteringsurfaces 64a, 66a lie in confronting relation to one another to definethe flow-metering orifice 62 therebetween. In the embodiment of FIG. 1,both of these flow-metering surfaces 64a, 66a are substantially flat.

In operation, the spring-biased valve member 36 functions to vent fuelvapor from the fuel tank 14 and valve assembly 10 only when the pressureexceeds a predetermined threshold level. Pressurized fuel tank vapor canexert a lifting force on the valve member 36 to urge the same againstthe spring 38, thereby lifting ring flange 42 off valve seat 39 to openthe annular passageway 48 between the valve member 36 and the interiorchamber wall 46. The pressurized fuel vapor is metered through orifice62 and then discharged from the valve housing 12 via outlet 22 andconducted to the atmosphere or to a treatment site such as aconventional fuel canister (not shown). The mass and configuration ofvalve member 36, the size of the various fluid-connecting passages, andthe spring constant of the spring 38 are selected to define thethreshold pressure level.

An annular skirt 67 extends into vapor discharge chamber 26 to providestop means for limiting upward travel of valve member 36. Skirt 67depends from a downwardly-facing surface of inner wall 20 in confrontingrelation to the top surface 52 of valve member 36. Skirt 67 is formed toinclude a plurality of slots 69 so as to permit fuel vapor to flow,thereby preventing flow shut-off. The height of skirt 67 is of suchdimension so as not to limit fuel vapor flow.

The flow rate of fuel vapor discharged is determined in part by thecross-sectional size of orifice 62. It will be appreciated that thissize changes during operation of the valve assembly 10 and is a functionat least of the relative position and configuration of the first andsecond flow-metering surfaces 64a, 66a. Thus, the pressure-vacuum valve30 functions to meter the flow rate of discharge fuel vapor, therebyregulating the maximum pressure allowable in the fuel tank 14.

The umbrella valve 34 regulates flow of ambient air or the like from theatmosphere or canister (not shown) into the chamber 26 and the fuel tank14 in response to suction caused by a vacuum in the fuel tank 14.Subatmospheric pressure in the fuel tank 14 will exert adownwardly-directed force to the resilient valve cover to at leastpartially open the umbrella valve 34 and draw ambient air or the likethrough outlet passage 22 and valve member apertures 40 into the chamber26. A vacuum created in the fuel tank 14, due to condensation or thelike, will act to draw fuel/fuel vapor from the canister (not shown)back into the tank 14. This will prevent the pressure in the fuel tank14 from dropping to zero and hold the tank pressure constant during anovernight vehicle cool-down or short-term vehicle parking.

In the embodiments of the invention illustrated in FIGS. 2-4, thoseelements referenced by numbers identical to those in FIG. 1 perform thesame or similar function. The pressure-relief and vacuum-relief featuresof these additional embodiments operate in essentially the same manneras the embodiment of FIG. 1.

The primary feature distinguishing each of the embodiments illustratedin FIGS. 2-4 is the configuration of the first and second flow-meteringsurfaces, 64b-d and 66b-d, respectively. In each case, the contour andshape of both flow-metering surfaces have been selected to meter theflow rate of fuel vapor through the orifice defined therebetween inaccordance with a predetermined engineering specification. In preferredembodiments, that predetermined engineering specification correlates thevolumetric flow rate of fuel vapor through the orifice to the magnitudeof the fuel vapor pressure existing in the fuel tank 14. It will beappreciated that by selecting a proper configuration for the first andsecond flow-metering surfaces and the proper spring constant for spring38, it is possible to discharge fuel through the flow-metering orificeat a selected flow rate corresponding to a selected fuel tank pressurein accordance with virtually any flow-pressure schedule.

Referring to the embodiment of FIG. 2, a pair of annular baffles 68, 70depend from downwardly-facing surface 56. First baffle 68 surroundssecond baffle 70 and extends into chamber 26 in an axially-inwarddirection toward the top surface 52 of valve member 36. Second baffle 70also extends downwardly into chamber 26 and is fixed in spaced-apartrelation to the surrounding first baffle 68 as shown in FIG. 2. Thefirst and second baffles 68, 70 cooperate to define an annular spacetherebetween for receiving the distal end 54 of upstanding skirt 50during movement of valve member 36 within chamber 26.

The first baffle 68 illustratively includes an annular,radially-inwardly facing surface 72 and the second baffle 70illustratively includes an annular, radially-outwardly facing surface74. Surfaces 72, 74 and the flat annular surface interconnectingsurfaces 72, 74 cooperate to define the first flow-metering surface 64b.In this embodiment, the second flow-metering surface 66b issubstantially flat.

Referring to the embodiment of FIG. 3, the first flow-metering surface64c is provided by the substantially flat surface 56. The distal end 54of skirt 50 has a top wall 75 and is formed to include a plurality ofcircumferentially-spaced slots 76 having inner walls 78. In thisembodiment, walls 75 and 78 cooperate to define the second flow-meteringsurface 66c.

In the embodiment of FIG. 3, each of the first and second flow-meteringsurfaces includes a radially inner downstream end at 90 in closeproximity to the outlet passage 22, an opposite radially outer upstreamend at 92, and an intermediate section extending therebetween. A firstdimension 86 separates opposing portions of the upstream ends and arelatively greater second dimension 88 separates opposing portions ofthe intermediate sections as shown in FIG. 3 due to the depth of theslots 76.

Referring to the embodiment of FIG. 4, a baffle 80 depends fromdownwardly facing surface 56 and extends into chamber 26 in an axiallyinward direction toward the top surface 52 of valve member 36. Baffle 80includes an annular, radially inwardly facing surface 82 which providesthe first flow metering surface 64d. The distal end 54 is formed toinclude an annular, radially outwardly-facing surface 84 which providesthe second flow-metering surface 66d.

Although the invention has been described in detail with reference tocertain preferred embodiments, variations and modifications exist withinthe scope and spirit of the invention as described and as defined in thefollowing claims.

What is claimed is:
 1. A flow-metering pressure-relief valve assemblyfor vehicle fuel tanks and the like, the assembly comprisinga valvehousing having an interior wall configured to define a chamber, inletopening means for admitting fuel vapor into the chamber, and outletopening means for exhausting fuel vapor from the chamber, the interiorwall providing a first flow-metering surface situated in close proximityto the outlet opening means, a valve seat attached to the valve housingand situated in the chamber to surround the inlet opening means, apressure-relief element in the chamber, the pressure-relief elementincluding a valve member having an inner surface confronting the inletmeans, and an upstanding skirt attached to the valve member and having adistal portion extending in an outward direction toward the outlet meansin spaced relation to the interior wall of the valve housing, the distalportion providing a second flow-metering surface which cooperates withthe first flow-metering surface to define a variable flow-meteringorifice therebetween, and biasing means for yieldably biasing the valvemember against the valve seat normally to close the inlet opening means,the second flow-metering surface being moved in relation to the firstflow-metering surface in response to relative movement of the valvemember and the valve seat to vary the size of the variable flow-meteringorifice, the first and second flow-metering surfaces havingpredetermined shapes that are configured to meter the flow ofpressurized fuel vapor through the variable flow-metering orifice inaccordance with a predetermined specification matching the flow rate offuel vapor exhausted through the outlet opening means to the magnitudeof the pressure exposed to the inner surface of the valve member, thevalve housing having a longitudinal axis and including a baffledepending from the interior wall and extending into the chamber in anaxially-inward direction toward the valve member, the baffle having aradially inwardly-facing surface providing the first flow-meteringsurface.
 2. A safety pressure-relief assembly for vehicle fuel tanks andthe like, the assembly comprisinga hollow valve housing including aninterior wall defining a valve chamber having an inlet and an outlet,the interior wall including a first flow-metering surface, and partitionmeans for dividing the valve chamber into a first portion communicatingwith the fuel tank via the inlet and a second portion communicating withthe outlet, the partition means including pressure-relief means fordischarging pressurized fuel vapor or the like from the first valvechamber portion to the second valve chamber portion to reduce fuel tankpressure, the pressure-relief means including a movable pressure-reliefvalve positioned in the valve chamber, the movable valve including asecond flow-metering surface situated in the second valve chamberportion confronting the first flow-metering surface in spaced relationto define a variable flow-metering orifice therebetween, the size of thevariable flow-metering orifice being functionally related to the spacingbetween the first and second flow-metering surfaces, the first andsecond flow-metering surfaces being configured to match the size of thevariable flow-metering orifice to the magnitude of pressure in the firstvalve chamber portion in accordance with a predetermined specificationso that the size of the variable flow-metering orifice variesautomatically as a function of pressure in the first valve chamberportion during operation of the pressure-relief means to regulate theflow of pressurized fuel vapor exhausted through the valve housingoutlet, the valve housing having a longitudinal axis and including abaffle depending from the interior wall and extending into the chamberin an axially-inward direction toward the valve member, the bafflehaving a radially inwardly-facing surface providing the firstflow-metering surface.
 3. A safety pressure relief assembly for vehiclefuel tanks and the like, the assembly comprisinga valve housing formedto include a valve chamber having an inlet and an outlet, the valvehousing providing a first flow-metering surface in the valve chamber. avalve seat in the valve chamber surrounding the inlet, a valve providinga second flow-metering surface, the valve being movably mounted in thevalve chamber to project the second flow-metering surface away from thevalve seat toward a position in close proximity to the firstflow-metering surface, the first and second flow-metering surfacescooperating to define a variable flow-metering space therebetween, thevariable flow-metering space having a size that varies during relativemovement of the first and second flow-metering surfaces to define avapor-discharge capacity of the assembly, and spring means for yieldablybiasing the valve against the valve seat normally to block flow of fuelvapor from the inlet to the outlet via the valve chamber and move thesecond flow-metering surface away from the first flow-metering surfacealong a path, the valve acting against the spring means to move thesecond flow-metering surface along the path toward the firstflow-metering surface to change the size of the variable flow-meteringspace in accordance with a predetermined specification functionallyrelating the size of the variable flow-metering space to pressureadmitted into the valve chamber via the inlet during exposure of thevalve to pressure in excess of a predetermined amount so that thevapor-discharge capacity of the variable flow-metering space is matchedto the magnitude of the valve-actuating pressure acting upon the valve,the valve housing having a longitudinal axis and including a baffledepending from the interior wall and extending into the chamber in anaxially-inward direction toward the valve, the baffle having a radiallyinwardly-facing surface providing the first flow-metering surface.